The invention relates to a process for the preparation of olefin polymers and copolymers using metallocenes containing specifically substituted indenyl ligands.
The use of chiral metallocenes as a catalyst component in the polymerization of olefins is known and gives highly isotactic polyolefins of high crystallinity and high melting point (cf. Angew. Chem. 97 (1985) 507, German Patent 40 35 886.0).
If achiral metallocenes are used, atactic polymers are obtained which, due to their unbalanced and inadequate product properties, are only of restricted industrial importance.
Of considerable interest are products whose property profile is between these two extremes.
The object was to find a suitable process or a suitable catalyst system which enables the preparation of polymers of reduced crystallinity, increased impact strength, increased transparency, good flow properties at the processing temperature, reduced melting point and high molecular weight.
The main applications of such polymers are plasticizer and lubricant formulations, hot-melt adhesive applications, coatings, seals, insulations, slush-molding compositions or sound-insulation materials.
The invention thus relates to a process for the preparation of an olefin polymer by polymerization or copolymerization of an olefin of the formula Raxe2x80x94CHxe2x95x90CHxe2x80x94Rb, in which Ra and Rb are identical or different and are a hydrogen atom or a hydrocarbon radical having 1 to 14 carbon atoms, or Ra and Rb, together with the atoms connecting them, can form a ring, at a temperature of from xe2x88x9260xc2x0 to 200xc2x0 C., at a pressure of from 0.5 to 100 bar, in solution, in suspension or in the gas phase, in the presence of a catalyst formed from a metallocene as transition-metal compound and a cocatalyst, wherein the metallocene is a compound of the formula I 
in which
M1 is a metal from group IVb, Vb or VIb of the Periodic Table,
R1 and R2 are identical or different and are a hydrogen atom, a C1-C10-alkyl group, a C1-C10-alkoxy group, a C6-C10-aryl group, a C6-C10-aryloxy group, a C2-C10-alkenyl group, a C7-C40-arylalkyl group, a C7-C40-akylaryl group, a C8-C40-arylalkenyl group or a halogen atom,
R3, R4 and R5 are identical or different and R3 and R4 and/or R5 are other than hydrogen and are a C1-C20-alkyl group, a C6-C20-aryl group, a C2-C10-alkenyl group, a C7-C40-arylalkyl group, a C7-C40-alkylaryl group or a C8-C40-arylalkenyl group, it also being possible for these radicals to be halogenated,
R4 or R5 may alternatively be hydrogen,
R6 is 
where
R9, R10 and R11 are identical or different and are a hydrogen atom, a halogen atom, a C1-C10-alkyl group, a C1-C10-fluoroalkyl group, a C6-C10-aryl group, a C6-C10-fluoroaryl group, a C1-C10-alkoxy group, a C2-C10-alkenyl group, a C7-C40-arylalkyl group, a C8-C40-arylalkenyl group or a C7-C40-alkylaryl group, or R9 and R10 or R9 and R11, in each case together with the atoms connecting them, form a ring,
M2 is silicon, germanium or tin,
R7 and R8 are identical or different and are as defined for R9, and
m and n are identical or different and are zero, 1 or 2, where m plus n is zero, 1 or 2.
Alkyl is straight-chain or branched alkyl. Halogen, (halogenated) denotes fluorine, chlorine, bromine or iodine, preferably fluorine or chlorine.
The indenyl ligands of the metallocene of the formula I used in the process according to the invention are substituted in the 2-position (R3) and in at least one of the two positions 5 (R4) and 6 (R5).
The catalyst to be used for the process according to the invention comprises a cocatalyst and a metallocene of the formula I.
In the formula I, M1 is a metal from group IVb, Vb or VIb of the Periodic Table, for example titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum or tungsten, preferably zirconium, hafnium or titanium.
R1 and R2 are identical or different and are a hydrogen atom, a C1-C10-, preferably C1-C3-alkyl group, a C1-C10-, preferably C1-C3-alkoxy group, a C6-C10-, preferably C6-C8-aryl group, a C6-C10-, preferably C6-C8-aryloxy group, a C2-C10-, preferably C2-C4-alkenyl group, a C7-C40-, preferably C7-C10-arylalkyl group, a C7-C40-, preferably C7-C12-alkylaryl group, a C8-C40-, preferably C8-C12-arylalkenyl group or a halogen atom, preferably chlorine.
R1, R4 and R5 are identical or different and R3 and R4 and/or R5 are other than hydrogen and are a C1-C20-, preferably C1-C10-alkyl group, a C6-C20-, preferably C6-C12-aryl group, a C2-C10-, preferably C2-C4-alkenyl group, a C7-C40-, preferably C7-C10-arylalkyl group, a C7-C40-, preferably C7-C12-alkylaryl group or a C8-C40-, preferably C8-C12-arylalkenyl group, it also being possible for these radicals to be halogenated.
R3, R4 and R5 are particularly preferably methyl, trifluoromethyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, benzyl, phenyl, tolyl, mesityl or xylyl.
R4 or R5 may alternatively be hydrogen; if this is the case, R5 is preferably hydrogen.
R6 is 
xe2x95x90BR9, xe2x95x90AlR9, xe2x80x94Gexe2x80x94, xe2x80x94Snxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO, xe2x95x90SO2, xe2x95x90NR9, xe2x95x90CO, xe2x95x90PR9 or xe2x95x90P(O)R9, where R9, R10 and R11 are identical or different and are a hydrogen atom, a halogen atom, a C1-C10-, preferably C1-C4-alkyl group, in particular a methyl group, a C1-C10-fluoroalkyl group, preferably a CF3 group, a C6-C10-, preferably C6-C8-aryl group, a C6-C10-fluoroaryl group, preferably a pentafluorophenyl group, a C6-C10-, preferably C1-C4-alkoxy group, in particular a methoxy group, a C2-C10-, preferably C2-C4-alkenyl group, a C7-C40-, preferably C7-C10-arylalkyl group, a C8-C40-, preferably C8-C12-arylalkenyl group or a C7-C40-, preferably C7-C12-alkylaryl group, or R9 and R10 or R9 and R11, in each case together with the atoms connecting them, form a ring.
M2 is silicon, germanium or tin, preferably silicon or germanium.
R6 is preferably xe2x95x90CR9R10, xe2x95x90SiR9R10, xe2x95x90GeR9R10, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x95x90SO, xe2x95x90PR9 or xe2x95x90P(O)R9 and particularly preferably xe2x95x90SiR9R10.
R7 and R8 are identical or different and are as defined for R9.
m and n are identical or different and are zero, 1 or 2, preferably zero or 1, where m plus n is zero, 1 or 2, preferably zero or 1.
The particularly preferred metallocenes are thus the compounds of the formula A 
where
M1 is Zr or Hf, in particular Zr; R1 and R2 are identical or different and are (C1-C3)-alkyl or chlorine; R3 and R4 are identical or different and are (C1-C10)-, preferably (C1-C4)-alkyl, which may be halogenated, in particular methyl or butyl, or (C6-C10) -aryl, in particular phenyl; R5 is hydrogen, (C1-C10)-, in particular (C1-C4)-alkyl, which may be halogenated, or (C6-C10)-aryl, in particular phenyl; and R9 and R10 are identical or different and are (C1-C10)-, preferably (C1-C4)-alkyl, in particular methyl, or (C6-C10)-, preferably (C6-C8)-aryl, in particular phenyl.
The chiral metallocenes are preferably employed as a racemate. However, it is also possible to use the pure R- or S-form. By means of these pure stereoisomeric forms, optically active polymer can be prepared. However, the meso-form of the metallocenes should be separated off, since the polymerization-active center (the metal atom) in these compounds is no longer chiral due to mirror symmetry at the central metal and is therefore incapable of producing a highly isotactic polymer. If the meso-form is not separated off, atactic polymer is formed in addition to isotactic polymers. For certain applicationsxe2x80x94for example soft moldingsxe2x80x94this may be entirely desirable.
Resolution of the stereoisomers is known in principle.
The above-described metallocenes can be prepared accordance with the following reaction scheme: 
The preparation processes are known from the literature; cf. Journal of Organometallic Chem. 288 (1985) 63-67, EP-A 320 762 and the working examples.
Starting compounds H2Rc and H2Rd are prepared, for example, as described in the working examples.
The cocatalyst used according to the invention is preferably an aluminoxane of the formula (II) 
for the linear type and/or of the formula (III) 
for the cyclic type, where, in the formulae (II) and (III), the radicals R12 may be identical or different and are a C1-C6-alkyl group, a C6-C18-aryl group, benzyl or hydrogen, and p is an integer from 2 to 50, preferably from 10 to 35.
The radicals R12 are preferably identical and are methyl, isobutyl, phenyl or benzyl, particularly preferably methyl.
If the radicals R12 are different, they are preferably methyl and hydrogen or alternatively methyl and isobutyl, where hydrogen and isobutyl are preferably present to the extent of 0.01-40% (number of radicals R14).
The aluminoxane can be prepared in various ways by known processes. One of the methods is, for example, to react an aluminum hydrocarbon compound and/or a hydridoaluminum hydrocarbon compound with water (in gas, solid, liquid or bound formxe2x80x94for example as water of crystallization) in an inert solvent (such as, for example, toluene). In order to prepare an aluminoxane containing different alkyl groups R12, two different trialkylaluminum compounds (AlR3+AlRxe2x80x23), in accordance with the desired composition, are reacted with water (cf. S. Pasynkiewicz, Polyhedron 9 (1990) 429 and EP-A 302 424).
The precise structure of the aluminoxanes II and III is unknown.
Depending on the preparation method, all aluminoxane solutions have in common a varying content of unreacted aluminum starting compound, which is in free form or as an adduct.
It is possible to preactivate the metallocene by means of an aluminoxane of the formula (II) and/or (III) before use in the polymerization reaction. This significantly increases the polymerization activity and improves the grain morphology.
The preactivation of the transition-metal compound is carried out in solution. The metallocene is preferably dissolved in a solution of the aluminoxane in an inert hydrocarbon. Suitable inert hydrocarbons are aliphatic or aromatic hydrocarbons. Preference is given to toluene.
The concentration of the aluminoxane in the solution is in the region of about 1% by weight to the saturation limits, preferably from 5 to 30% by weight, in each case based on the total solution. The metallocene can be employed in the same concentration, but is preferably employed in an amount of from 10xe2x88x924 to 1 mol per mole of aluminoxane. The preactivation time is from 5 minutes to 60 hours, preferably from 5 to 60 minutes. The reaction temperature is from xe2x88x9278xc2x0 C. to 100xc2x0 C., preferably from 0xc2x0 to 70xc2x0 C.
The metallocene can also be prepolymerized or applied to a support. For the prepolymerization, the (or one of the) olefin(s) employed in the polymerization is preferably used.
Examples of suitable supports are silica gels, aluminum oxides, solid aluminoxane or other inorganic support materials. Another suitable support material is a polyolefin powder in finely divided form.
Compounds of the formulae RxNH4-xBRxe2x80x24, RxPH4-xBRxe2x80x24, R3CBRxe2x80x24 or BRxe2x80x23 can be used according to the invention as suitable cocatalysts instead of or in addition to an aluminoxane. In these formulae, x is a number from 1 to 4, preferably 3, and the radicals R are identical or different, preferably identical, and are C1-C10-alkyl or C6-C18-aryl, or 2 radicals R, together with the atom connecting them, form a ring, and the radicals Rxe2x80x2 are identical or different, preferably identical, and are C6-C18-aryl, which may be substituted by alkyl, haloalkyl or fluorine.
In particular, R is ethyl, propyl, butyl or phenyl and Rxe2x80x2 is phenyl, pentafluorophenyl, 3,5-bistrifluoromethylphenyl, mesityl, xylyl or tolyl (cf. EP-A 277 003, EP-A 277 004 and EP-A 426 638).
When the abovementioned cocatalysts are used, the actual (active) polymerization catalyst comprises the product of the reaction of the metallocene and one of said compounds. This reaction product is therefore prepared first, preferably outside the polymerization reactor, in a separate step using a suitable solvent.
In principle, suitable cocatalysts are according to the invention any compounds which, due to their Lewis acidity, are able to convert the neutral metallocene into a cation and stabilize the latter (xe2x80x9clabile coordinationxe2x80x9d). In addition, the cocatalyst or the anion formed therefrom must not undergo any further reactions with the metallocene cation formed (cf. EP-A 427 697).
In order to remove catalyst poisons present in the olefin, purification by means of an alkylaluminum compound, for example AlMe3 or AlEt3, is advantageous. This purification can be carried out either in the polymerization system itself, or the olefin is brought into contact with the Al compound before addition to the polymerization system and subsequently removed again.
The polymerization or copolymerization is carried out in a known manner in solution, in suspension or in the gas phase, continuously or batchwise, in one or more steps, at a temperature of from xe2x88x9260 to 200xc2x0 C., preferably from 30xc2x0 to 80xc2x0 C. Olefins of the formula Raxe2x80x94CHxe2x95x90CHxe2x80x94Rb are polymerized or copolymerized. In this formula, Ra and Rb are identical or different and are a hydrogen atom or an alkyl radical having 1 to 14 carbon atoms. In the preparation of homopolymers, one of the two radicals Ra and Rb is preferably other than hydrogen However, Ra and Rb, together with the carbon atoms connecting them, can form a ring. Examples of such olefins are ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, norbornene and norbornadiene. In particular, propylene and ethylene are polymerized.
If necessary, hydrogen is added as molecular weight regulator and/or to increase the activity. The total pressure in the polymerization system is from 0.5 to 100 bar. Polymerization is preferably carried out in the industrially particularly relevant pressure range of from 5 to 64 bar.
The metallocene is used in a concentration, based on the transition metal, of from 10xe2x88x923 to 10xe2x88x928 mol, preferably from 10xe2x88x924 to 10xe2x88x927 mol, of transition metal per dm3 of solvent or per dm3 of reactor volume. The aluminoxane is used in a concentration of from 10xe2x88x925 to 10xe2x88x921 mol, preferably from 10xe2x88x924 to 10xe2x88x922 mol, per dm3 of solvent or per dm3 of reactor volume. The other cocatalysts mentioned are used in approximately equimolar amounts with respect to the metallocene. In principle, however, higher concentrations are also possible.
If the polymerization is carried out as a suspension or solution polymerization, an inert solvent which is customary for the Ziegler low-pressure process is used. For example, the polymerization is carried out in an aliphatic or cycloaliphatic hydrocarbon; examples of these which may be mentioned are propane, butane, pentane, hexane, heptane, isooctane, cyclohexane and methylcyclohexane.
It is furthermore possible to use a benzine or hydrogenated diesel oil fraction. Toluene can also be used. The polymerization is preferably carried out in the liquid monomer.
If inert solvents are used, the monomers are metered in as gases or liquids.
The polymerization can have any desired duration, since the catalyst system to be used according to the invention exhibits only a slight time-dependent drop in polymerization activity.
The process according to the invention is distinguished by the fact that the metallocenes described give polymers having the desired property profile, preferably in the industrially relevant temperature range between 30xc2x0 and 80xc2x0 C. with high polymerization activity. These polymers preferably have a molecular weight Mw of  greater than 80,000, in particular  greater than 100,000 g/mol, a melting point of  less than 145xc2x0 C. and a molecular weight dispersity Mw/Mn of xe2x89xa63.5, in particular xe2x89xa62.8.
The examples below are intended to illustrate the invention in greater detail.
The following abbreviations are used:                     VI        =                  viscosity          ⁢                      xe2x80x83                    ⁢          index          ⁢                      xe2x80x83                    ⁢          m          ⁢                      xe2x80x83                    ⁢                      cm            3                    ⁢                      /                    ⁢          g                                                                                                                                  M                    w                                    =                                      weight                    ⁢                                          xe2x80x83                                        ⁢                    average                    ⁢                                          xe2x80x83                                        ⁢                    molecular                    ⁢                                          xe2x80x83                                        ⁢                    weight                                                                                                                        in                  ⁢                                      xe2x80x83                                    ⁢                  g                  ⁢                                      /                                    ⁢                  mol                                                                                                                                                                        M                        w                                            /                                              M                        n                                                              =                                          molecular                      ⁢                                              xe2x80x83                                            ⁢                      weight                      ⁢                                              xe2x80x83                                            ⁢                      dispersity                                                        ⁢                                      xe2x80x83                                                                                ⁢                      xe2x80x83                    }                ⁢                                                            determined                ⁢                                  xe2x80x83                                ⁢                by                                                                                        gel                ⁢                                  xe2x80x83                                ⁢                permeation                                                                        chromatography                                                                                    m            .            p            .                    =                      melting            ⁢                          xe2x80x83                        ⁢            point                          ,                  determined          ⁢                      xe2x80x83                    ⁢          by          ⁢                      xe2x80x83                    ⁢          DSC                                        (                              heating            /            cooking                    ⁢                      xe2x80x83                    ⁢          rate          ⁢                      xe2x80x83                    ⁢          20          ⁢          xc2x0          ⁢                      xe2x80x83                    ⁢                                    C              .                        /            min                          )                                          II          =                      isotactic            ⁢                          xe2x80x83                        ⁢            index            ⁢                          xe2x80x83                        ⁢                          (                              II                =                                  min                  +                                                            1                      /                      2                                        ⁢                                          xe2x80x83                                        ⁢                    mr                                                              )                                      ,                                determined        ⁢                  xe2x80x83                ⁢        by        ⁢                  xe2x80x83                ⁢                                           13                    ⁢          C                ⁢                  -                ⁢        NMR        ⁢                  xe2x80x83                ⁢        spectroscopy                                          n          iso                =                              isotactic            ⁢                          xe2x80x83                        ⁢            block            ⁢                          xe2x80x83                        ⁢            length                    =                      1            +                                          2                ⁢                                  xe2x80x83                                ⁢                mm                            mr                                          
Synthesis of the metallocenes used in the examples:
General remarks:
All solvents were dried by customary processes, unless otherwise stated. All reagents, apart from dimethyldichlorosilane, were employed without pretreatment. Dimethyldichlorosilane was distilled before use over potassium carbonate in a stream of nitrogen. Some of the reactions were followed by gas chromatography under uniform conditions: temperature program: 120xc2x0-220xc2x0 C., 10xc2x0 C./min, 220xc2x0-270xc2x0 C., 40xc2x0 C./min, helium, 200 kPa, column: HP-1, 50 m.
In order to support assignment of 13C-NMR signals, in some cases DEPT135-NMR spectra were recorded. The phase position is shown in parenthesis after the value for the chemical shift. (0) denoted quaternary C, (+) methyl or methine and (xe2x88x92) methylene.